Conventionally, various types of pillows have been proposed. For example, pillows for adjusting the height of head rest in respect to the substrate by using adjusting bolt, jack, link mechanism or the like are known. Pillows allowing a desired shape of head rest surface by choosing holes of any height and introducing respectively both ends of a plurality of metal bars into side plates having a number of holes and disposed with a certain interval or the like have been proposed.
However, as the adjustment is made on the side, the conventional height adjustment is unattractive and its structure exposes the pillow side.